Anomalous reactivity of anti‐T cell sera on spleen cells from T‐cell‐deprived mice and on mitogen‐stimulated nude mice spleen cells

Recent results have shown that various alloantisera which react in the expected fashion on lymphocyte populations can react anomalously against cultured tumor cell populations because of the presence of contaminating antibodies against murine leukemia virus (MLV) antigens. Since it is now known that activation of MLV can occur in certain types of dividing lymphocyte populations, anti-T cell sera were tested on lymphoid cell populations in which T cells were absent or greatly reduced in numbers, but where activation of MLV in the B cell population would be expected. Whereas normal, freshly harvested, nude mice spleen cells were unreactive, in vitro:stimulation of these cells with the B cell mitogen, lipopolysaccharide, led to a high degree of sensitivity to the cytotoxic effects of anti-T alloantisera or heteroantisera. Spleen cells from adult thymectomized, lethally-irradiated, bone marrow-reconstituted mice also showed unexpected reactivity with the anti-T cell sera. In both cases, reactivity was noted only if absorbed rabbit serum was used as a complement source in the cytotoxic assays. The anomalous anti-B cell activity of the anti-T cell sera could be removed by absorption with relatively small numbers of cells from Thy-negative cultured tumor cell lines, including fibrosarcomas, but not by absorption with thymocytes. Hence, activated or stimulated B cells may react strongly with allo-or hetero- anti-T cell sera under certain conditions, and this anomalous reactivity appears unrelated to the presence of the anti-T cell antibodies in the sera.